Universal Mobile Telecommunications System (UMTS) is a 3G Mobile Telecommunications System that employs Wideband Code Division Multiple Access (WCDMA) air interface technology. It is developed mainly in a WCDMA/GSM (Global System for Mobile Communications) Global Standardization Organization, Third Generation Partnership Project (3GPP).
In 3GPP UMTS Standards, a User Equipment (UE) may have two modes, an IDLE mode and an RRC Connected mode, according to whether a Radio Resource Control (RRC) connection is established. The UE on which the RRC connection is not established with a UMTS Universal Terrestrial Radio Access Network (UTRAN) is in an IDLE mode, and the UE in the IDLE mode can only be distinguished via a Non-Access Stratum (NAS) identification, such as International Mobile Subscriber Identity (IMSI). The UE on which RRC connection is established with the UTRAN is in the RRC Connected mode, and a Radio Network Temporary Identity (RNTI) is allocated to the UE in this mode as an identification of the UE on a common transport channel.
However, for the UE in the RRC Connected mode, it may have different states according to the hierarchy of RRC connection and the type of transport channel that can be used by the UE. The UE in a CELL_PCH state, a CELL_FACH state or a CELL_DCH state can be distinguished on cell hierarchy, and the UE in a URA_PCH state can be distinguished on UTRAN RegisterArea (URA) hierarchy. The UE in the CELL_DCH state is allocated a dedicated physical channel, and the UE can use a dedicated transport channel, a shared channel and a combination thereof. The UE in the CELL_FACH state is required to consecutively monitor a common transport channel (FACH, Forward Access Channel) downstream, and a default common channel (RACH, Reverse Access Channel) is allocated upstream. The UE in the CELL_PCH or the URA_PCH state monitors a Page Channel (PCH) via a related PICH (Page Indicator Channel) in a manner of Discontinuous Reception (DRX), and no upstream activities are performed by the UE in these two states.
In 3GPP UMTS Standards, when a UE is in different modes and states, cells with different frequencies are to be measured according to the measurement control information or system information received and the reception quality of the current cell, so that processes such as cell reselection and cell handover can be performed. The trigger condition for performing Inter-Frequency measurement by the UE in the IDLE state, CELL_PCH state, URA_PCH state or CELL_FACH state is the system information received and the reception quality of the current cell. However, the trigger condition for performing Inter-Frequency measurement by the UE in the CELL_DCH state is the measurement control information transmitted by the system. Usually, for a UE without double receivers, because receiving and decoding for signals with two different frequencies cannot be supported simultaneously, reception of signals in the current cell will be interrupted when Inter-Frequency measurement is performed by the UE.
At the same time, with the development of 3G mobile telecommunications technology, the demands for mobile telecommunications services of users are not just limited to voice service. Because the 3G mobile telecommunications system can provide a much higher data transmission rate than the second generation (2G) mobile telecommunications system can, a large number of multimedia services spring up, such as visual telephone, picture download and high-speed Internet surfing. Some application services require that a plurality of users can receive the same data simultaneously, such as video on-demand, television broadcast, video conference, online education and interactive games.
The concept of multicast and broadcast is introduced into the 3G mobile telecommunications system to effectively utilize mobile telecommunications network resources. Multicast and Broadcast Service is a technology to transfer the same data from one data source to a plurality of destinations. Therefore, the WCDMA/GSM Global Standardization Organization, 3GPP, puts forward Multimedia Broadcast/Multicast Service (MBMS), which means a Point to Multipoint service that sends the same data from one data source to a plurality of users on mobile telecommunications networks, so that network resources can be shared, and the utilization of network resources, especially the utilization of air interface resources, can be improved.
In the MBMS service, data transfer modes between a UE and a UTRAN can be classified into two types: a Point to Point (PTP) mode and a Point to Multipoint (PTM) mode. The PTP mode is used for MBMS multicast mode, and the UE in the RRC connection mode under multicast mode receives control information via a Dedicated Control Channel (DCCH) and receives data information via a Dedicated Traffic Channel (DTCH). The PTM mode is used for MBMS broadcast or multicast mode, and the UE in this mode receives data information via an MBMS point-to-multipoint Traffic Channel (MTCH) and receives control information via an MBMS point-to-multipoint Control Channel (MCCH).
In MBMS service, the control information is transmitted via an MCCH in the PTM mode and the MBMS control information provided on the MCCH includes service information, access information and wireless bearer information, etc. For simplicity, the MBMS control information provided on the MCCH is abbreviated as “MCCH information”. The MCCH information can be classified into critical information and non-critical information. The critical information includes MBMS adjacent cell information, MBMS service information and MBMS wireless bearer information and the non-critical information includes MBMS access information.
The MCCH information is transmitted using a fixed schedule, and is transmitted periodically based on a “Repetition Period” to improve reception reliability. A “Modification Period” is an integral multiple of the “Repetition Period”. The critical information can only be modified during the Modification Period when the MCCH information is transmitted for the first time. MBMS modification information will be transmitted by the UTRAN at the beginning of each Modification Period. The modification information includes the MBMS service identification of the MCCH information modified in the Modification Period. The MBMS modification information is repeated at least once during each Repetition Period of the Modification Period; However, the non-critical information can be modified at any time. Further, the MBMS access information is transmitted periodically based on an “Access Info Period” which is an integral multiple of the “Access Info Period”. FIG. 1 is a schematic diagram showing the correlation among the “Repetition Period”, “Modification Period” and “Access Info Period” during the time when the MCCH information is transmitted by the UTRAN.
The values of the Modification Period, the Access Info Period and the Repetition Period are successive as follows:
Modification Period: The range of coefficient m is (7 . . . 10), and a Modification Period MP=2m×frame length.
Access Info Period: The range of coefficient a is (0 . . . 3), and a Access Info Period AIP=(MP/2a)×frame length.
Repetition Period: The range of coefficient r is (0 . . . 3), and Repetition Period RP=(MP/2r)×frame length.
In a cell, a UE obtains information of related MBMS service by receiving the MCCH information, obtains the access information of the desired services by receiving access information in the MCCH information, and sends MBMS service request information to the UTRAN according to the access information.
When in the CELL_FACH state, the UE performs the Inter-Frequency measurement during the frame(s) with the frame System Frame Number (SFN) fulfilling the following equation:SFN div N=C_RNTI mod M_REP+n×M_REP  (1)
Where
N represents the number of 10 ms frames of Transmission Timing Interval (TTI) of the Forward Access Channel (FACH) having the largest TTI on Secondary Common Control Physical Channel (SCCPCH) that bears non-MBMS logical channels, and the SCCPCH is monitored by the UE;
M_REP represents a measurement occasion cycle length, and M_REP=2k. According to the above equation (1), the Repetition Period of the measurement occasion of N frames is N×M_REP frames;
Where, k is the coefficient of FACH measurement occasion cycle length, which is read from the information element “FACH measurement occasion info” contained in system information 11 or system information 12;
C_RNTI (cell radio network temporary identity) is the C-RNTI value of the UE; and
n=0, 1, 2 . . . , as long as SFN is less than its maximum value.
The corresponding values of N and k are:
NTTIk13, 4, 5, 622, 3, 4, 5
Therefore, the UE can obtain an SFN which fulfills the condition defined by the above equation 1 by calculating according to equation (1), and perform Inter-Frequency measurement on the SFN, and interrupt the reception of the MBMS of current cell during Inter-Frequency measurement.
Because the minimum value of the “Access Info Period” for a UTRAN to transmitted the MCCH information is 0.16 s, the values in the numeric area are all multiples of this minimum value; and according to the above equation (1), when the FACH TTI of a UE in the CELL_FACH state is 10 ms and k=3, Inter-Frequency measurement is performed once every 80 ms, and the measurement duration is 10 ms. As a result, the following problems may appear:
(1) The time for Inter-Frequency measurement of some UEs overlaps constantly the time when a UTRAN transmits the MCCH information, and because the UE needs to perform Inter-Frequency measurement during this overlapping time, the UE cannot receive important MCCH information in this overlapping time.
(2) To avoid the problem in (1), the time for Inter-Frequency measurement of the UE may be prevented from overlapping constantly the transmission time of the MCCH information by the UTRAN via changing the C-RNTI of the UE, but when there are too many UEs performing Inter-Frequency measurement, considering the difference among the transmission time points of the MCCH information in each cell, the UTRAN needs to modify the C-RNTI of each UE so as to avoid the problem that the time for Inter-Frequency measurement of each UE overlaps constantly the transmission time of the MCCH information. As a result, the allocation and schedule complexity of the UTRAN may be increased.
When in the IDLE state, CELL_PCH state and URA_PCH state, when the UE supports DRX function, Inter-Frequency should be measured at least every (Ncarrier-1)×TmeasureFDD when performing Inter-Frequency measurement. Parameter Ncarrier refers to the number of different frequencies measured; the final Inter-Frequency measurement value should be obtained by the terminal by averaging at least two Inter-Frequency measurement values, and in the Inter-Frequency measurement values for averaging, there should be at least two measured values whose interval is at least TmeasureFDD/2. The corresponding parameters are specifically as follows:
DRX cycle0.080.160.320.641.282.565.12length [s]Tmeasure0.64 (80.64 (4)1.28 (4)1.28 (2)1.28 (1)2.56 (1)5.12 (1)FDD[s]DRX cycles)(number of DRXcycles)
Therefore, if the UE supports a MBMS service in the IDLE state, CELL_PCH state or URA_PCH state, when Inter-Frequency measurement is to be performed, the UE needs to perform Inter-Frequency measurement periodically, so as to obtain an Inter-Frequency measurement value. When UE without double receivers performs Inter-Frequency measurement, the reception of the current cell MBMS service may also be interrupted.
It can be seen from the above table that a multiple relation exists between the period in which UE performs Inter-Frequency measurement to obtain an Inter-Frequency measurement value and the period in which a UTRAN transmits the MCCH information, and the UE does not consider the relation with the transmission time of the MCCH information when setting sampling time points of Inter-Frequency measurement. As a result, the sampling time of Inter-Frequency measurement performed by UE may overlap constantly the transmission time of the MCCH information, so the UE may never receive important and requisite MCCH information.
In the CELL_DCH state, a WCDMA FDD terminal performs Inter-Frequency measurement in a compressed mode indicated by the UTRAN, and the technical principle of the compressed mode is as shown in FIG. 2, i.e. data transmission rate will be increased when the UTRAN sends some frames (data sent every 10 ms is referred to as 1 frame), and the data sent in 10 ms originally will now be sent in a time of less than 10 ms, so that the spared time will be used by the UE to perform Inter-Frequency measurement. It is controlled by the UTRAN completely how and when to increase the transmission rate.
When the WCDMA FDD terminal receives MBMS PTM service in the CELL_DCH state, the UTRAN controls the UE to perform Inter-Frequency measurement by transmitting information bearing the compressed mode. If it's supported to receive MBMS control information on MCCH by the UE, when the UE without double receivers performs Inter-Frequency measurement, reception of the current cell MCCH information may be interrupted; and the time for performing Inter-Frequency measurement is entirely indicated by the compressed mode information sent by the UTRAN.
However, when the compressed mode of UE Inter-Frequency measurement is configured by the UTRAN, the transmission period of the MCCH information is not considered at all. Since the compressed mode information is used by the UE repeatedly and the MCCH information is also periodically transmitted, the Inter-Frequency measurement time indicated by the compressed mode may overlap constantly the transmission time of the MCCH information. As a result, the UE may never receive important and requisite MCCH information when performing Inter-Frequency measurement in the Inter-Frequency measurement time designated by the UTRAN.
The problems existing during the Inter-Frequency measurement performed by the UE in the above various states also occur when Inter-RAT measurement is performed.